1. Field of the Invention
The present invention relates to a noncorrosive cleaning composition for metal oxide-type, post-etch residues which contain the combination of (1) selected solvents; (2) selected amines; (3) selected corrosion inhibitors; (4) selected redox reagents; optionally (5) water.
2. Description of the Prior Art
The photoresist stripper art is replete with numerous references to stripper combinations containing both a polar solvent and an amine compound. The presence of an amine in photoresist stripper compositions has been judged to be essential to effectively remove resist film cross-linked by baking, plasma etching, ion implantation, or other LSI device manufacturing processes. However, amine-type photoresist strippers sometimes have a serious problem of corrosion, especially with aluminum substrates.
It is believed that this corrosion proceeds by the ionization of water by the amine in post-stripping water rinses, as residual stripper solution may be retained on the substrate surface and/or substrate carrier after the stripping step. In other words, the amine component of the stripper composition does not corrode the substrate, but may trigger water to cause the corrosion.
To solve this problem, an intermediate rinse step with an organic solvent has been used between the stripping step and the post-stripping rinse with water. For example, isopropyl alcohol is known to be useful for this purpose. However, such intermediate rinses are not necessarily desirable because overall stripping operation becomes more complicated and, furthermore, an additional solvent waste is produced. Accordingly, if amine-type strippers are to be further employed, there is a need to solve this corrosion problem without intermediate organic solvent washes. The present invention provides such a solution.
During anisotropic plasma etching processes for via contacts, metal patterns, and passivation openings, "sidewall residues" are frequently deposited on the resist sidewall. After the oxygen plasma ashing of photoresist films, these residues become metal oxides. Incomplete removal of these residues interfere with the pattern definition and/or complete filling of via-holes.
Several different chemistries have been identified for removing the post-etch residues, in particular of the metal oxide type. For example, alkaline developers such as aqueous tetramethyl-ammonium hydroxide (TMAH) are known to attack aluminum so that an aluminum oxide can be etched with TMAH. However, other types of the post-etch residues associated with multi-metal systems such as Al/Si/Cu cannot be so easily removed with TMAH. TMAH also is ineffective on residues from polysilicon plasma etch processes.
The metal oxide type sidewall residues can also be removed with: (1) a mixture of HF and ethylene glycol ether or (2) a mixture of nitric acid, acetic acid, and hydrofluoric acid. These solutions require extreme process control to prevent excessive attack of critical metal and oxide layers. In some device structures, these solutions are not useable because of their nonselective attack mechanisms.
Recently, Wai M. Lee described at The Interconnects, Contact Metallization and Multilevel Metallization Symposium (183rd Spring Meeting) of The Electrochemical Society, Inc. in Honolulu, Hi., May 16-21, 1993, that a hydroxylamine-containing stripper composition can remove some kinds of the sidewall residues.
Although hydroxylamine has a potential to remove the metal oxide type of the post-etch residues, it is not stable upon heating.
Accordingly, hydroxylamine is not suitable for the use of stripping of photoresist films or removing of the post-etch residues at higher temperatures.
Illustrative references suggesting photoresist stripper composition containing the combination of a polar solvent and an amine compound are the following:
1. U.S. Pat. No. 4,617,251, which issued to Sizensky et al. on Oct. 14, 1986, teaches a positive photoresist stripping composition containing (A) selected amine compound (e.g., 2-(2-aminoethoxy)-ethanol; 2-(2-aminoethylamino)-ethanol; and mixtures thereof) and (B) selected polar solvents (e.g., N-methyl-2-pyrrolidinone, tetra-hydrofurfuryl alcohol, isophorone, dimethyl sulfoxide, dimethyl adipate, dimethyl glutarate, sulfolane, gamma-butyrolactone, N,N-dimethyl-acetamide and mixtures thereof). The reference further teaches that water as well as dyes or colorants, wetting agents, surfactants and antifoamers may be added into this composition.
2. U.S. Pat. No. 4,770,713, which issued to Ward on Sep. 13, 1988, teaches a positive photoresist stripping composition containing (A) a selected amide (e.g., N,N-dimethyl acetamide; N-methyl acetamide; N,N-diethyl acetamide; N,N-dipropyl acetamide; N,N-dimethyl propionamide; N,N-diethyl butyramide and N-methyl-N-ethyl propionamide) and (B) selected amine compound (e.g., monoethanolamine, monopropanolamine, methylamino-ethanol). The patent also teaches this stripper may optionally contain a water miscible nonionic detergent (e.g., alkylene oxide condensates, amides and semi-polar nonionics).
3. U.S. Pat. No. 4,786,578, which issued to Neisius et al. on Nov. 22, 1988, teaches a rinse solution used after a photoresist stripper, said rinse solution containing (A) a nonionic surfactant (e.g., ethoxylated alkylphenol, fatty and ethoxylate, fatty alcohol ethoxylate or ethylene oxide/propylene oxide condensate) and (B) an organic base (e.g., mono-, di-, or tri-ethanolamine).
4. U.S. Pat. No. 4,824,762, which issued to Kobayashi et al. on Apr. 25, 1989, teaches photoresist stripping post-rinse solution containing (A) glycol ether (e.g., diethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether) and (B) an aliphatic amine (e.g., monoethanolamine or tri-isopropylamine).
5. U.S. Pat. No. 4,824,763, which issued to Lee on Apr. 25, 1989, teaches positive-working photoresist stripping composition containing (A) triamine (e.g., diethylene-triamine) and (B) non-polar solvent (e.g., N-methyl-2-pyrrolidone, dimethylformamide, butyrolactone, aliphatic hydrocarbons, aromatic hydrocarbons, chlorinated hydrocarbons).
6. U.S. Pat. No. 4,904,571, which issued to Miyashita et al. on Feb. 27, 1990, teaches printed circuit board photoresist stripper composition containing (A) a solvent (e.g., water, alcohols, ethers, ketones, chlorinated hydrocarbons and aromatic hydrocarbons); (B) an alkaline compound dissolved in said solvent (e.g., primary amines, secondary amines, tertiary amines, cyclic amines, polyamines, quaternary ammonium amines, sulfonium hydroxides, alkali hydroxides, alkali carbonates, alkali phosphates and alkali pyrophosphates); and (C) a borohydride compound dissolved in said solvent (e.g., sodium borohydride, lithium borohydride, dimethyl amine borone, trimethyl amine borone, pyridane borone, tert-butyl amine borone, triethyl amine borone, and morpholine borone).
7. German Published Patent Application No. 3828513, which published on Mar. 1, 1990 and is assigned to Merck patent GMBH, teaches a positive and negative photoresist stripper composition containing (A) an aprotic polar solvent (e.g., 1,3-dimethyl-2-imidazolidinone or 1,3-dimethyl-tetrahydro-pyrimidinone); and (B) an organic base (e.g., alkanolamine).
8. Japanese Published Pat. Application No. 56-115368, which was published on Sep. 10, 1981 and is assigned to San Ei Chemical Industries, KK, teaches a photoresist stripping composition containing (A) nonionic surface activator (e.g., a polyethylene glycol ether); (B) organic solvent (e.g., cyclohexanone); and (C) either a swelling agent (e.g., polyethylene glycol) or penetrant (e.g., 2-aminoethanol).
9. Japanese Published Pat. Application No. 63-208043, published on Aug. 29, 1988, teaches a positive-working photoresist stripper composition containing (A) 1,3-dimethyl-2-imidazolidinone; (B) a water-soluble organic amine (e.g., monoethanolamine, 2-(2-aminoethoxy)-ethanol, triethylene(tetramine). The application also teaches a surfactant may be added to the stripper.
10. Japanese Published Patent Application No. 1-081949, which published on Mar. 28, 1989 and is assigned to Asahi Chemical, teaches a positive-working photoresist stripper composition containing (A) gamma-butyrolactone, N-methyl-formamide, N,N-dimethylformamide, N,N-dimethyl-acetoamide or N-methylpyrrolidone; (B) an amino alcohol (e.g., N-butyl-ethanolamine and N-ethyldiethanolamine); and (C) water.
11. Japanese Published Patent Application No. 4-350660, which is assigned to Texas Instruments, Japan and Kanto Chemical, Inc., teaches a stripper for positive photoresists comprising (A) 1,3-dimethyl-2-imidazolidinone (DMI), (B) dimethyl-sulfoxide (DMSO) and (C) a water-soluble amine (e.g., monoethanolamine or 2-(2-aminoethoxy)ethanol wherein the amount of the water-soluble amine is 7-30% by weight.
12. U.S. Pat. No. 5,279,791, which issued to Lee on Jan. 18, 1994, teaches a stripping composition for removing resists from substrates containing (A) hydroxylamine (e.g., NH.sub.2 OH); (B) at least one alkanolamine; and optionally (C) at least one polar solvent.
13. Japanese Published Patent Application No. 7-28254, which is assigned to Kanto Chemical, Inc., teaches a stripper for the sidewall residues comprising (a) a selected compound from sugar alcohols, isopropylalcohol, dimethylsulfoxide, and 1,3-dimethyl-2-imidazolidininone; (b) alkanolamine; (c) water; and optionally (d) quaternary ammonium hydroxides.
None of these references suggest a complete solution for removing post-etch residues, particularly for the metal oxide type, without corrosion.